Does fasted training help burn fat?

The early bird gets the six-pack. Which is why, before dawn, gyms resonate to men putting in a pre-breakfast pump. They might not be able to lift as much. They might give up earlier. But ask them why they're there and they'll explain that fasted training is the quick route to a lean physique.

Their logic seems sensible: take away your body's favoured fuel and it scrambles for another way to keep going. When you hit the gym without eating, you're already running low on its preferred propellant, glycogen, so fat has to fill the gap. Bye bye spare tyre. But like that other simple equation – calories in - calories out = weight – it's a theory that doesn't add up.

The Fast and the Spurious

First, a caveat. The blubber-burning benefits to training fasted are proven; a study from Northumbria University found that working out before breaking your fast increases fat oxidation by more than 20% during exercise. But as any Men's Health man knows, what happens on the gym floor is only a tiny piece of the fitness-building puzzle.

Intense training is the pilot light that ignites your fat-burning fires. But to spark it, you need fuel. Attempt Tabata without eating and, as soon as your glycogen stores are depleted, you'll hit the wall.

As you know from the overweight guys whose high-intensity interval training means cycling between rest and 30 seconds light jogging, for the I and T to be effective, you need to up the H and I. Try revving your engine to red without fuel in the tank and expect to stall.

That's why endurance athletes espouse occasional fasted training – the key word being, occasional. Working out starved mimics that point in the race when your glycogen is gone but the finish line is still miles away. Over time, it learns to target fat for fuel. But that's a back-up generator. Come race day, you load up on carbs to power you as far as possible before your second-string engine kicks in, then hope it takes you to the tape.

Fasted training, slower burn

If you haven't coaxed this kind of performance out of your body before, then don't expect it to happen automatically. Instead, your pre-feed legs session will be curtailed when your first set of deadlifts wipes you out and you can't complete the second. That's not a muscle-building protocol you'll hear many athletes recommending.

When your alarm sounds, you're pulsing with the stress hormone cortisol, which breaks down your body to provide energy. Unfortunately, it's not discerning enough to separate fat from muscle. Provide something else to digest and cortisol dissipates. Stay hungry and it continues to gobble up your biceps, so your gains become the energy that keeps your whole body going.

If you're trying to ditch the last couple of percent of body fat then briefly resorting to fasted training might get you there. But it's not sustainable. Fill your tank then work until it's empty. You'll not just reach the finish line - you'll build a body worthy of the podium.

3 ways to speed up fat loss by slowing down

1. When researchers from the University of Texas set carb-fuelled athletes against fasted counterparts, they found the breakfast-skippers experienced a slight uptick in fat oxidation only after 90 minutes of exercise. By which time you could have fit in a lie-in, breakfast, and a HIIT session.

2. Dosing with lasagne is also effective ahead of legs day, according to research from Mississippi State University, which found loading athletes with 1g of carbs per kg of bodyweight increased how much force they could put out, and how long they could lift for. Both of which means more gains.

3. Even if you're not training fasted, long sessions can still turn your body catabolic. To outflank this muscle-guzzling, lace your pre-workout with BCAAs to limit the damage. And throw in a handful of dried fruit as well, to ensure you've got the sugars that make getting up an hour earlier worth it.

Dylan Jones is a strength and condition expert with a speciality in bio-mechanical correction. As an ex-Army instructor, he’s done his fair share of early morning training and knows exactly why it’s not worth setting your alarm

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